This invention relates to densified gas based systems, more particularly to divided pressure vessel apparatus for carbon dioxide based systems and methods of using same.
An important operational consideration for many, if not all, carbon dioxide processing systems is throughput, which may be defined as the amount of articles or materials that may be processed in a given period of time. In various processes that utilize carbon dioxide as a solvent, multiple solvent baths may be used to improve operational efficiency by increasing throughput. For example, in a carbon dioxide based dry cleaning system, it may be desirable to provide pre-washing, washing, rinsing, and distillation operations. The pre-wash, wash, and rinse solutions may each have a different chemical composition. If a single tank were used to store the various baths, the composition of the solution in the tank would need to be adjusted between each operation, which may increase cycle time and decrease throughput. By utilizing a tank for storing a pre-wash solution, a separate tank for storing wash solution, another separate tank for storing a rinse solution, and yet another separate distillation tank, the dry cleaning system may be able to cycle through the operations of pre-washing, washing, rinsing, and distillation in a more timely manner.
U.S. Pat. No. 5,267,455 to Dewees et al. proposes a dry cleaning system particularly suited for employing supercritical carbon dioxide as the cleaning fluid consisting of a sealable cleaning vessel containing a rotatable drum adapted for holding soiled substrate, a cleaning fluid storage vessel, and a separate gas vaporizer vessel for recycling used cleaning fluid.
While utilizing multiple solvent baths in carbon dioxide based systems may improve operational efficiency, the increased capital costs associated with such systems may outweigh some of the operational benefits. Carbon dioxide based systems may be required to operate at elevated pressures in order to maintain the carbon dioxide solvent in either a liquid or a supercritical state. As a result, each of the separate tanks must be a stamp coded and certified pressure vessel, which can be quite expensive. Additionally, each of the separate tanks must be in constant fluid communication with a pressure relief valve. Thus, the capital cost of constructing a carbon dioxide based system having multiple solvent baths may outweigh some, if not all, of the operational benefits that may be gained by utilizing such a system.
WO 97/33031 proposes a storage/still vessel that both distills and stores the liquid gas for use in another cleaning cycle. The storage/still vessel includes a tube located within an inner cavity of an outer tank. At the top of the tube is an opening that provides fluid communication between the inner cavity and an inner chamber of the tube. The bottom of the tube has a one-way control valve that allows the liquid gas to flow from the inner cavity to the inner chamber. The vessel has a heating element that can heat and vaporize the liquid gas within the inner chamber of the tube. The still vaporizes the liquid gas within the tube, which causes liquid to flow from the inner cavity to the inner chamber. Vaporized liquid gas condenses and falls into the inner cavity, which then forms a layer of distilled xe2x80x9ccleanxe2x80x9d liquid, on top of a layer of undistilled xe2x80x9cdirtyxe2x80x9d liquid. The cycle is continued until the level of dirty liquid falls below the one way control valve.
WO 97/33031 does not provide an apparatus utilizing a carbon dioxide based solvent that will allow two or more fluids having different chemical compositions to be stored and/or processed within the same pressure vessel while maintaining the different chemical compositions of the two or more fluids.
According to the present invention, divided pressure vessels for use in a carbon dioxide based system are provided. Divided pressure vessels of the present invention may allow multiple solvent baths each having a different chemical composition to be stored and/or processed in a single pressure vessel while maintaining the different chemical compositions of the multiple solvent baths. Thus, divided pressure vessels of the present invention may provide the improved operational efficiency of a carbon dioxide based system having multiple solvent baths while decreasing the capital costs that may be associated with such systems. Methods of utilizing such divided pressure vessels in processing systems employing carbon dioxide based solvents are also be provided.
According to the present invention, methods of utilizing a divided storage vessel include transferring a first densified gas based treating solution from a first liquid chamber in a divided storage vessel having a plurality of liquid chambers to a processing vessel, returning the first treating solution from the processing vessel to the divided storage vessel, transferring a second carbon dioxide based treating solution having a composition different from the first treating solution from a second liquid chamber in the divided storage vessel to a processing vessel, and returning the second treating solution from the processing vessel to the divided storage vessel. The processing system may be a batch processing system, a semi-batch processing system, or a continuous processing system.
In embodiments of the present invention, the methods of utilizing a divided storage vessel include contacting an article in the processing vessel with the first treating solution, and contacting the article in the processing vessel with the second treating solution. The first treating solution may be a pre-wash solution, a wash solution, or a coating solution, and the second treating solution may be a wash solution, a coating solution, or a rinse solution. The articles may be various substrates including, but not limited to, fabric substrates, metal substrates, and electronic devices, to name just a few. The operation of contacting the article with the wash solution may include removing polymeric materials, such as resins, adhesive, coatings, and inks, from the article.
In other embodiments of the present invention, at least one of the first or second treating solutions is an impregnating solution that includes an impregnating agent. The operation of contacting the article with the impregnating solution includes impregnating the article with the impregnating agent. The article may be a porous material and the impregnating agent may be insect treatments, pigments, strength enhancers, water repellants or pollution repellants.
In still other embodiments of the present invention, at least one of the first or the second treating solutions is an extracting solution, and the operation of contacting the article with the extracting solution includes extracting a substance from the article using the extracting solution.
In yet other embodiments of the present invention, at least one of the first or the second treating solutions is a developing solution. The operation of contacting the article with the developing solution includes developing a resist on a semiconductor substrate using the developing solution.
In other embodiments of the present invention, the methods of utilizing a divided storage vessel includes the operation of synthesizing a chemical compound by combining the first treating solution with the second treating solution. The first treating solution is a first reacting solution that includes a first reactant and the second treating solution is a second reacting solution that includes a second reactant.
In still other embodiments of the present invention, the methods of utilizing a divided storage vessel includes polymerizing one or more monomers by combining the first treating solution with the second treating solution where the first treating solution includes a first monomer and the second treating solution includes an initiator or a second monomer.
In yet other embodiments of the present invention, the methods of utilizing a divided storage vessel includes purifying a chemical compound by combining the first treating solution comprising the chemical compound with a third treating solution substantially devoid of liquid carbon dioxide.
Cleaning methods are also provided by the present invention. Cleaning methods according to the present invention include transferring a first densified gas based treating solution from a first liquid chamber of a divided working tank to a wash tank containing an article, contacting the article with the first liquid, returning the first treating solution from the wash tank to the divided working tank, transferring a second densified gas based treating solution from a second liquid chamber of the divided working tank to the wash tank, contacting the article with the second treating solution, and returning the second treating solution from the wash tank to the divided working tank. The method may include storing a plurality of densified gas based treating solutions present as two-phase systems in a divided storage vessel having a plurality of liquid chambers that share a common vapor space.
Dry cleaning methods are also provided by the present invention. Dry cleaning methods according to the present invention include transferring a first densified gas based dry-cleaning solution from a first liquid chamber of a divided working tank to a wash tank containing a dry-cleanable article, contacting the dry-cleanable article with the first liquid, returning the first dry-cleaning solution from the wash tank to the divided working tank, transferring a second densified gas based dry-cleaning solution from a second liquid chamber of the divided working tank to the wash tank, contacting the dry-cleanable article with the second dry-cleaning solution, and returning the second dry-cleaning solution from the wash tank to the divided working tank. The method may include storing a plurality of densified gas based dry-cleaning solutions present as two-phase systems in a divided storage vessel having a plurality of liquid chambers that share a common vapor space.
In embodiments of the present invention, the first dry-cleaning solution is a pre-wash solution, a wash solution, or a coating solution, and the second dry-cleaning solution is a wash solution, a coating solution, or a rinse solution.
In other embodiments of the present invention, the operation of returning the first dry-cleaning solution from the wash tank to the divided working tank includes returning the first dry-cleaning solution from the wash tank to the first chamber of the divided working tank. The operation of returning the second dry-cleaning solution from the wash tank to the divided working tank includes returning the second dry-cleaning solution from the wash tank to the second chamber of the divided working tank. The second liquid may be distilled in the second liquid chamber to form still bottoms and vapor consisting essentially of carbon dioxide.
In still other embodiments of the present invention, dry cleaning methods include transferring a first volume of the first dry-cleaning solution from the first liquid chamber into a third liquid chamber of the divided working tank before transferring a first dry-cleaning solution from the first liquid chamber to the wash tank. The operation of transferring a first volume includes equilibrating the liquid levels in the first liquid chamber and the third liquid chamber. The dry cleaning methods include transferring a second volume of the first dry-cleaning solution from the third liquid chamber into the first liquid chamber after transferring a first dry-cleaning solution from the first liquid chamber to the wash tank, such that a third volume of the first dry-cleaning solution remains in the third liquid chamber. The operation of transferring a second volume includes equilibrating the liquid levels in the first liquid chamber and the second liquid chamber. The second volume of dry-cleaning solution is transferred from the first liquid chamber to the wash tank. The third volume of the first dry-cleaning solution is distilled in the third liquid chamber. The distilling operation includes boiling the third volume of the first dry-cleaning solution in the third liquid chamber to form still bottoms and carbon dioxide vapor, condensing the vapor from the third liquid chamber to form liquid carbon dioxide, collecting the liquid in the second liquid chamber, and purging the still bottoms from the third liquid chamber. The operation of returning the first dry-cleaning solution from the wash tank to the divided working tank includes returning the first dry-cleaning solution from the wash tank to the first liquid chamber. The operation of returning the second dry-cleaning solution from the wash tank to the divided working tank includes the step of returning the second dry-cleaning solution from the wash tank to the first liquid chamber. Alternatively, the operation of returning the second dry-cleaning solution from the wash tank to the divided working tank may include the step of returning the second dry-cleaning solution from the wash tank to the third liquid chamber. The second dry-cleaning solution may be distilled in the third liquid chamber. A coating adjunct may be added to the second dry-cleaning solution before, during or after the operation of transferring the second dry-cleaning solution from the second liquid chamber to the wash tank.
In yet other embodiments of the present invention, dry cleaning methods include transferring a first volume of the first dry-cleaning solution from the first liquid chamber into a third liquid chamber of the divided working tank before transferring a first dry-cleaning solution from the first liquid chamber to the wash tank. The first volume of the first dry-cleaning solution is transferred from the third liquid chamber to the wash tank before transferring a first dry-cleaning solution from the first liquid chamber to the wash tank. A pre-wash adjunct may be added to the first volume of the first dry-cleaning solution to form a pre-wash solution. The pre-wash adjunct may be added before, during, or after transferring the first volume of the first dry-cleaning solution from the third liquid chamber to the wash tank. The methods include contacting the article with the pre-wash solution, and returning the pre-wash solution from the wash tank to the third liquid chamber of the divided working tank before transferring a first dry-cleaning solution from the first liquid chamber to the wash tank. The pre-wash solution may be distilled in the third liquid chamber. The distilling operation may occur during at least one of the foregoing operations. The operation of returning the second dry-cleaning solution from the wash tank to the divided working tank may include returning the second dry-cleaning solution from the wash tank to the first liquid chamber.
A divided working tank for use in a carbon dioxide based system is also provided by the present invention. The divided working tank includes an exterior wall defining an interior volume and capable of withstanding an internal pressure of at least about 500 psig, a first dividing member extending from an interior surface of the exterior wall and defining a first and a second liquid chamber in the divided pressure vessel, the first and the second liquid chambers sharing a common vapor space, and a first treating solution consisting essentially of densified gas positioned in the first liquid chamber. The densified gas is preferably liquid carbon dioxide.
In embodiments of the present invention, the divided working tank includes a second dividing member defining a third liquid chamber. The third liquid chamber shares the common vapor space with the first and the second liquid chambers. The second liquid chamber is positioned between the first liquid chamber and the third liquid chamber. A heating element is operatively associated with the third liquid chamber.
In other embodiments of the present invention, the divided working tank includes a first opening in the exterior wall adjacent the first liquid chamber for liquid transfer into and/or out of the first liquid chamber, a second opening in the exterior wall adjacent the second liquid chamber for liquid transfer into and/or out of the second liquid chamber, a third opening in the exterior wall adjacent the third liquid chamber for liquid transfer into and/or out of the third liquid chamber, and a fourth opening in the exterior wall adjacent the common vapor space for fluid transfer into and/or out of the common vapor space. The fourth opening is preferably positioned above the third liquid chamber.
In still other embodiments of the present invention, the divided working tank includes a second densified gas based treating solution positioned within the second liquid chamber. The first and the second treating solutions have different compositions.
A dry cleaning system employing a carbon dioxide based solvent is also provided by the present invention. The dry cleaning system includes a divided working tank configured to store a plurality of densified gas based dry-cleaning solutions having different compositions as described above and a wash tank configured to contact a dry-cleanable article to be cleaned with one or more of the plurality of dry-cleaning solutions. The wash tank is in fluid communication with the divided working tank.
In embodiments of the present invention, the cleaning system may include a liquid transfer system that provides liquid communication between the divided working tank and the wash tank, and a vapor transfer system that provides vapor communication between the divided working tank and the wash tank. The first, the second, and the third openings of the divided working tank may be in liquid communication with the liquid transfer system. The fourth opening of the divided working tank may be in fluid communication (i.e., liquid and/or vapor communication) with the vapor transfer system. The vapor transfer system may include a condenser that is in fluid communication with the fourth opening of the exterior wall of the divided working tank.
In embodiments of the present invention, methods of utilizing a divided storage vessel include transferring a first treating adjunct from a first chamber in a divided storage vessel having a plurality of chambers that share a common vapor space to a processing vessel, transferring a densified fluid comprising a liquid densified gas or a supercritical fluid into the processing vessel, removing the first treating adjunct from the processing vessel, transferring a second treating adjunct having a composition different from the first treating adjunct from a second chamber in the divided storage vessel to the processing vessel, and removing the second treating adjunct from the processing vessel.
In other embodiments of the present invention, methods of utilizing a divided storage vessel include charging a first densified fluid comprising a liquid densified gas or a supercritical fluid into a processing vessel, removing the first densified fluid from the processing vessel, charging the first densified fluid into a first liquid chamber in a divided storage vessel having a plurality of liquid chambers that share a common vapor space, charging a second densified fluid comprising a liquid densified gas or a supercritical fluid into the processing vessel, removing the second densified fluid from the processing vessel, and charging the second densified fluid into a second liquid chamber in the divided storage vessel.
Methods and apparatus according to the present invention may therefore provide the operational efficiency associated with a densified gas based processing system having multiple solvent baths stored in various separate tanks at a lower capital costs than such processing systems. It will be understood that the present invention may be embodied as methods and apparatus and combinations thereof.